mongodb增删查改

document定义

关系型数据库的一条记录可以认为是一行.mongodb是非关系型数据库,它的一条记录是一个"文档"(document).mongodb的document是key-value结构的集合.

插入document

一次插入一个document

db.users.insertOne(
    {
        name: "sue",
        age:26,
        status:"pending"
    }
)

db代表当前数据库,users是一个collection, 3个key-value的结构组成一个document.
一次插入多个document:

db.inventory.insertMany([
   { item: "journal", qty: 25, size: { h: 14, w: 21, uom: "cm" }, status: "A" },
   { item: "notebook", qty: 50, size: { h: 8.5, w: 11, uom: "in" }, status: "A" },
   { item: "paper", qty: 100, size: { h: 8.5, w: 11, uom: "in" }, status: "D" },
   { item: "planner", qty: 75, size: { h: 22.85, w: 30, uom: "cm" }, status: "D" },
   { item: "postcard", qty: 45, size: { h: 10, w: 15.25, uom: "cm" }, status: "A" }
]);

查找document

要想查找collection中的所有数据,执行

db.inventory.find( {} )

查找status为D的document:

db.inventory.find( { status: "D" } )

查找status为D或者A的document:

db.inventory.find( { status: { $in: [ "A", "D" ] } } )

查找status为A且qty小于30的document:

db.inventory.find( { status: "A", qty: { $lt: 30 } } )

其中$lt是小于(less than)的意思.
查找status为A或者qty小于30的document:

db.inventory.find( { $or: [ { status: "A" }, { qty: { $lt: 30 } } ] } )

更新document

把item为journal的document,size.uom修改为om,status修改为P.

db.inventory.updateOne(
   { item: "journal" },
   {
     $set: { "size.uom": "om", status: "P" }
   }
)

更新多条记录

db.inventory.updateMany(
   { "qty": { $lt: 50 } },
   {
     $set: { "size.uom": "in", status: "P" },
     $currentDate: { lastModified: true }
   }
)

更新qty小于50的document的size.uom和status.
替换整个文档:

db.inventory.replaceOne(
   { item: "paper" },
   { item: "paper", instock: [ { warehouse: "A", qty: 60 }, { warehouse: "B", qty: 40 } ] }
)

删除document

删除所有document:

db.inventory.deleteMany({})

删除status为A的document:

db.inventory.deleteMany({ status : "A" })

限制mongo占用内存大小

mongod --dbpath=/data/mongodb/ --rest --fork --logpath=/data/mongodb/mongo.log --logappend --wiredTigerCacheSizeGB 10

只安装客户端

在/etc/yum.repos.d/mongodb-org-4.0.repo里添加

[mongodb-org-4.0]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.0/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-4.0.asc

然后

yum install mongodb-org-shell